The present invention relates to a sheet material feeding device for feeding a sheet material or a plurality of sheet materials one by one. The materials may be recording materials, copying materials, original documents or the like fed to a recording station, copying station, reading station or the like in a recording apparatus, an image forming apparatus, an image reading apparatus or the like such as a printer, a copying machine, a printing apparatus, a facsimile machine, a scanner or the like, and also relates to a recording apparatus using the same.
Such a sheet material feeding device is equipped with a double feed preventing mechanism to prevent two or more sheets from being fed simultaneously to assure separation of sheets for one-by-one feeding of the sheets.
Known sheet material feeding devices with the double feed preventing mechanism include a retarding roller type which uses a roller reversely rotated with respect to the sheet feeding direction through a torque limiter, a returning lever type which uses a returning lever which is operated each time a predetermined number of the sheets are fed to return the leading end of the sheet material to a predetermined position, and a type in which these two types are combined.
One of the examples of the returning type is disclosed in U.S. Pat. No. 5,997,198, in which a feeding roller is rotated in the sheet material feeding direction through a driving source for the sheet material feeding device, and after the feeding operation is completed by one full-rotation of the feeding roller, the driving source is rotated in the opposite direction to actuate the returning lever to returns the leading end of the sheet material to a predetermined position.
An example of the combination type is disclosed in Japanese Laid-open Patent Application Hei 10-167502 in which when a stacking means for stacking the sheet materials is urged in a releasing direction of releasing the contact of the stacked sheet material to the feeding roller, a retarding roller which is rotated in the opposite direction (opposite to the feeding direction) through a torque limiter is separated. Substantially simultaneously, the returning lever is actuated to returns the leading end of the sheet material to a predetermined position.
However, in such conventional examples, some limitations are imposed to actuate the mechanism for preventing the double feeding of the sheet materials.
More particularly, in the sheet material feeding device using the retarding roller, the use is made with the torque limiter for which a releasing torque has to be maintained at a proper level, and the roller has to be reversely rotated at all times during the feeding operation. These requirements make the mechanism complicated, bulky and expensive. In addition, the returning lever has to be actuated only after completion of the series of the feeding operations, and therefore, an additional time is required for the returning lever operation with the result of longer time required for the double feeding prevention.
Accordingly, it is a principal object of the present invention to provide a sheet material feeding device and a recording apparatus wherein the double feeding of the sheet materials are assuredly prevented with a simple structure not leading to bulkiness or expensiveness of the apparatus, and which does not require a complicated control or long time for the double feeding prevention.
According to an aspect of the present invention, there is provided a sheet material feeding device comprising a sheet material stacking means for stacking sheet materials; a feeding roller for feeding the sheet material stacked on said sheet material stacking means; a separation roller, driven by said feeding roller, for separating a sheet material from said sheet materials; a separation roller holder for rotatably holding said separation roller, said separation roller holder is movable by rotation thereof between a position in which said separation roller is contacted to said feeding roller and a position in which said separation roller is away from said feeding roller; and returning means for returning a sheet material or sheet materials other than the sheet material separated out by said separation roller to said sheet material stacking means.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.